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> For a complete documentation index, see https://bcdtravel.ferndocs.com/air/guides/introduction/application-logic/llms.txt.
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# Application logic

## Data encoding

Please ensure that all the data sent via GET methods is percent encoded.

## Common request parameters

### Required parameters

These parameters must be passed with every API call:

| Name        | Type   | Required | Description                                                                                                          |
| ----------- | ------ | -------- | -------------------------------------------------------------------------------------------------------------------- |
| `api_key`   | string | Yes      | Your public API key. Example: `api_key=testkey`.                                                                     |
| `timestamp` | string | Yes      | The UNIX (UTC) timestamp created by your application for this request (in seconds). Example: `timestamp=1388774110`. |
| `nonce`     | string | Yes      | A unique cryptographic identifier created by your application to secure the request. Must be 32 characters or less.  |

### Optional parameters

These parameters are encouraged with every request:

| Name          | Type   | Required | Description                                                                                                                                                                                                                                                                  |
| ------------- | ------ | -------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `locale`      | string | No       | Language preference. Valid values: `en_US`, `fr_FR`, `de_DE`, `es_ES`, `it_IT`, `pt_PT`, `ja_JP`, `ko_KR`. Default is `en_US`.                                                                                                                                               |
| `session_id`  | string | No       | A unique user session identifier created by your application. Do not use the real user's session identifier. Useful for logging and troubleshooting requests by user. Note: `<`, `>`, `&` are prohibited.                                                                    |
| `customer_ip` | string | No       | The IP address of your user. Allows us to determine the user's location for fraud recovery and analytics.                                                                                                                                                                    |
| `user_agent`  | string | No       | The user agent (device, application, or browser) of your user. Required to get discounted mobile rates. Must be properly encoded, unique to each request, and no more than 32 characters. Mobile format: `{App Name}/{App Version} ({OS} {OS Version}) [APP or MOBILE_APP]`. |

> Understand request parameters, data encoding, and application logic for the Air API.